Sealing structure for a tank which is closed by a cap

ABSTRACT

A sealing structure is provided by an O-ring disposed on a tank, suitable for use in a sprayer, and closed by a cap adapted to carry a pump actuated by a handle which extends into the tank when the cap closes the tank. The O-ring is maintained in a notch between a rim around an open end of a neck of the tank and a shelf extending outwardly from the rim. The cap has a shoulder forming an exterior angle approximately the same as the interior angle between the rim and the shelf on the neck. The shoulder has a chamfered surface which truncates the exterior angle of the shoulder. When the cap is connected to the tank by external threads around the neck and internal threads below the shoulder, the O-ring is compressed in two directions against the rim and against the shelf on the neck of the tank thereby providing an effective compression seal between the cap and the tank.

The present invention relates to a sealing structure which connects a cap and a tank in sealed relationship. The invention is especially suitable for closing a pressurized tank for a sprayer with a cap from which the sprayer pump may depend into the tank, the sealing structure being capable of resisting pressures of the type maintained in sprayers, for example, of about 60 psi.

It is a feature of the invention to provide a sealing structure which utilizes an O-ring captured on a tank which provides a seal between the tank and a cap thereby providing more reliable and more easily implemented sealing structure than is the case where the O-ring is located in the cap.

Sealing structures having O-rings which have heretofore been used in caps which close pressurizable tanks in sprayers are illustrated by way of example in FIGS. 4 and 4A. The cap is shown separated from the tank in FIG. 4A and screwed on in FIG. 4B. There, the cap and the tank are closed by threads which are screwed down to bring a tapered surface at the end of a neck on the tank into engagement with an O-ring captured in an internal grove in the top of the cap above the internally threaded collar thereof. The implementation of the internally notched cap and the tapered end of the neck of the tank requires complex machining or molding operations, and is therefore more difficult to implement than with an O-ring sealing structure provided by the invention where the O-ring is disposed on the tank rather than on the cap. Also, with the O-ring in the cap, it is difficult to discern whether the O-ring is actually in the cap because it is hidden from view, and also because in most caps, the O-ring and the cap are of the same color, for example, black.

An O-ring in the cap is maintained in place by radially inward compression by the tapered end of the neck of the tank when the cap is screwed on the tank. If the cap is unscrewed while the tank is pressurized, the pressurized fluid, gas or liquid, in the tank can enter behind the O-ring and eject the O-ring from its notch in the cap. The O-ring then can fall into the tank and must be fished out of the tank and reinstalled. This is an operational disadvantage with sealing structures having O-rings in the cap.

It is the feature of this invention to provide an effective, reliable, and easily implementable sealing structure for a tank by a cap where the O-ring is disposed on the tank rather than in the cap.

Briefly described, a sealing structure provided by the invention may be implemented by an O-ring disposed where a preferably notched rim meets a shelf at the top, or open end of a neck extending from a tank. The cap may be screwed on the neck by inter-engaging internal and external threads in the cap and around the neck of the tank, respectively. The cap is formed with a shoulder having a radial portion extending inwardly of the cap from an interior peripheral wall and meeting the wall at a corner forming an external angle equal approximately to the internal angle between the rim and the shelf on the neck of the tank in which the O-ring is seated. This external angle of the shoulder is truncated preferably at approximately 45°, thereby providing a chamfered edge at the corner. When the cap is screwed on the neck of the tank, the shoulder moves into the internal angle of the neck, where the O-ring is captured, and the chamfered corner compresses the O-ring in two directions, rather than merely one direction as in the sealing structure of FIG. 4, namely downwardly against the shelf and radially against the rim. An effective and reliable seal is thereby provided by the O-ring capable of withstanding pressure in the tank and not subject to any pressurized fluid which may be released from the tank through the cap from a partially pressurized tank, when the cap is being opened.

The foregoing and other objects, features, and advantages of the invention will become more apparent from the following description of a preferred embodiment thereof which is shown in FIGS. 1-3; the prior art design where the O-ring is in the cap being shown in FIG. 4. In the drawings:

FIGS. 1 and 1A is an exploded view illustrating the upper part of a tank, the O-ring and the cap of a sealing structure provided in accordance with the invention, where the O-ring is separated from the tank in FIG. 1 and on the tank in FIG. 1A;

FIG. 2 is a sectional view of the cap tank and O-ring in assembled relationship, the section being taken through a plane extending diametrically through the cap, O-ring and tank and along the line indicated at 2-2 in FIG. 1 when viewed in the direction of the arrows at the end of the section line;

FIG. 3 is an enlarged, fragmentary sectional view also along the line of 2-2 where the cap tank and O-ring are in assembled relationship to provide the sealing structure of the invention; and

FIGS. 4A and 4B are sectional views of a sealing structure where the cap contains the O-ring, where the cap is separated from the tank prior to being screwed on to the tank neck in FIG. 4A and screwed on the tank in FIG. 4B, and which is discussed above; the views being marked “prior art”.

Referring more particularly to the drawings, there is shown a tank 10 which is adapted to be pressurized by means of a pump (not shown) which is mounted in a cap 12, for example, screwed into an internal threaded section 14 (see FIG. 2) with the handle of the pump extending through an opening 16 in the cap. The cap also has a fixture 18 for receiving a pressure relief valve (not shown). The tank 10, the cap 12, and an O-ring 20 are used in the sealing structure. The sealing structure is provided by the structure in the neck 22 of the tank and an internal threaded collar 24 of the cap 12 which has features which compress the O-ring against the neck 22. This sealing structure is indicated generally at 26 in FIG. 3. This cap structure 24 is connected to the central section 30 of the cap 12. An array of external and internal ribs 32 and 34 connect the central section to a collar 36 having internal threads 38 which mesh with external threads 40 on the neck 22 of the tank 10. The tank may be blow molded from plastic, such as high-density polypropylene. The cap may be injection molded from polypropylene.

A skirt 42 is disposed around the internally threaded central collar section 36 of the cap. The skirt is knurled on its exterior so as to enable the cap to be grasped and screwed on and off the tank 10. The O-ring 20 is preferably made of lubricant impregnated elastic (rubber) material. The impregnating lubricant enables the surfaces of the cap which contact the O-ring to glide thereon as the ring is compressed, so that the O-ring remains captured in place in a notch 44 in a rim 46 at the upper end of the neck 22. The notch is provided by a lip 48 at the upper end of the neck. The neck is formed with a shelf 50 which extends radially outward from the rim 46 and defines an internal angle of approximately 90° between the shelf 50 and the rim 46. The O-ring 20 is captured at the apex of this 90° angle and is restricted to the notch 44 by the lip 48.

The rim 46 is internally offset radially inwardly toward the axis of the tank in order to correspond to the internal offset of a chamfered corner of a shoulder 52 of the central collar 24 of the cap which lies above the threads 38 thereof. This shoulder 52 has a radial portion 56 which opposes the shelf 50 and a peripheral sleeve-like section 58 which opposes the rim 46. The angles where the sleeve 58 and radial part 52 of the shoulder at and meet at an angle of approximately 90°, that is an angle approximately equal to the angle of the shelf 50 to the rim 46.

As shown in FIG. 3, when the cap is screwed onto the tank 10 with the threads 38 and 40, the chamfered surface 60 of the shoulder 52 engages and compresses the O-ring, not only downwardly against the shelf 50, but also radially against the rim 44. An effective and reliable seal is therefore provided by the O-ring and the sealing structure 26.

The sealing structure provides for static compression of the O-ring where it comes in contact with a tapered or chamfered surface on the shoulder in the cap, compressing the O-ring against the vertical rim and the horizontal shelf. Internal pressure created inside the tank applies pressure to the seal. This internal pressure acts to deform the O-ring slightly, extruding it into the gap between the tank and cap further improving the seal. Sealing is further enhanced due to the internal pressure acting to move the inner walls of the tank outward increasing the internal force between the tank and O-ring. The O-ring is stretched slightly over the tank lip 48 diameter which is stepped inwardly to form the notch 44 to retain the O-ring and keep it in place. The cap thread 38 preferably has two full thread turns resulting in friction between the cap and tank eliminating the tendency of the cap to unscrew itself. The ribs 32 and 34 on the cap minimize distortion caused by the internal pressure in the tank on the cap closing the tank, thus the integrity of the O-ring seal surfaces.

From the foregoing description it will be apparent that there has been provided improved sealing structure, especially adapted for use with pressurized tank which are closed by a cap. Variations and modifications in the herein described sealing structure within the scope of the invention will undoubtedly suggest themselves skilled in the art. Accordingly, the foregoing description should be taken as illustrative and not in a limiting sense. 

1. A sealing structure for a tank having a neck and a cap having a collar engagable with said neck, said sealing structure comprising an O-ring, said neck having a rim around an end of said neck which is closed by said cap and a shelf extending outwardly from said rim, said O-ring being disposed around said rim and seated on said shelf, said collar having an internal shoulder disposed about said rim and opposed to said shelf when said end of said neck is closed by said cap, said shoulder having a chamfered corner engaging and compressing said O-ring two directions, namely against said rim of said neck and against said shelf when said cap closes said tank.
 2. A sealing structure according to claim 1 wherein said rim and said shelf are disposed at an internal angle of about 90° and said shoulder has an interior periphery defining an exterior angle of about 90° truncated by said tapered surface.
 3. The sealing structure according to claim 1 wherein said rim has notch therein extending to a lip, said lip extending from said end of said neck which is closed by said cap, said O-ring being captured in said notch.
 4. The sealing structure according to claim 1 wherein said cap is internally threaded between an open end thereof and said shoulder, said neck is externally threaded with threads which engage internally threaded cap to close the tank with said shoulder around said rim and shelf and said O-ring compressed therebetween.
 5. The sealing structure according to claim 4 further comprising a coupling for a pump which depends from said cap into said tank when closed by said cap, said coupling structure being radially inward of said shoulder, an opening in said end of said cap which closes said tank for passage of a shaft from a handle which operates said pump to pressurize said tank. 